The present invention relates generally to optical devices and specifically to wearable visual aids.
The performer of fine, detailed work, such as surgery or watchmaking, is helped by visual aid devices that reduce eye fatigue and increase visual acuity. One such visual aid device is disclosed in U.S. Pat. No. 4,834,525 issued May 30, 1989 to Vansaghi. Referring to FIG. 1, a visual aid device 10 features telescopes 121, 123 mounted on eyeglass frames 111 via carrier lenses 117, 119. Carrier lenses 117, 119 may be prescription lenses to provide visual correction to permit a visually impaired user to see through the portions of carrier lenses 117, 119 peripheral to the areas covered by telescopes 121, 123. Since carrier lenses 117, 119 may be prescription lenses, visual correction is provided for such peripheral viewing. In addition, referring also to FIG. 2, corrective lenses 137 may be affixed to bushings 127 to provide visual correction during viewing through telescopes 121, 123.
Visual aid device 10 may be designed specifically for a particular user to accommodate his anatomical and visual correction needs. However, the ideal optical characteristics of such devices depend on the particular task as well as on the particular user. For example, a cardiovascular surgeon may require telescopes having different optical characteristics than required by a dentist. Such optical characteristics include the focusing or working distance, the distance from the user's eyes to the region being observed, and the magnification factor. Moreover, the same specialist might require telescopes with different optical characteristics for different tasks, such as a dentist who performs both chair-side surgery and laboratory bench work. Such customization may require that separate devices be purchased for each user or task. Such multiple purchases involve considerable expense, especially when carrier lenses 117, 119 and corrective lenses 137 are manufactured especially for a particular user.
To solve this problem, visual aid device 10 has been designed with interchangeable telescopes. Telescopes 121, 123 are removably mounted on respective carrier bushings 125, 127 by means of bayonet-type mounts. The bayonet-type mount includes a front portion 131 of bushing 127, which is a female member that receivably mates with a male member 139 at an end of telescope 123. An interior bore 141 of bushing 127 has a circumferential groove 143 for receiving mating tabs 145 of male member 139. An outer wall 132, which bounds circumferential groove 143, has slots 152 to permit mating tab 145 to enter circumferential groove 143. Telescope 123 is pushed toward bushing 127 as male member 139 is inserted in interior bore 141 until mating tabs 145 pass through slots 152. Telescope 123 is then rotated 1/8th of a turn to slide mating tabs 145 in circumferential groove 143 and lock behind solid portions 153 of outer wall 132. A detente mechanism (not shown) locks mating tabs 145 in position so that telescope 123 cannot thereafter be rotated easily. Thus, telescope 123 cannot fall out.
Though the prior-art device of FIGS. 1 and 2 permits lenses to be interchanged, positive locking of the lens may not be achieved. If telescope 123 is rotated insufficiently to engage the detente device, telescope 123 will stay in place for a time, but it will not be positively locked in place. If not locked in place, telescope 123 can fall out of interior bore 141 during use. If telescope 123 should fall out during surgery or some other delicate work, great hardship could result.
In addition to making it possible for telescope 123 to fall out of place during use, the bayonet-type mount requires telescope 123 to be rotationally as well as axially aligned with the bushing, inserted and then twisted, which is inconvenient.
Another problem with the prior art visual aids is the difficulty of compensating for axial misalignment of telescopes 121, 123. Telescopes invariably incorporate some axial misalignment due to manufacturing tolerances causing the line of sight of the telescope to be different from that for which the mount is ideally configured. Such misalignment can result in poor imaging and/or eye fatigue.
Still another problem with the prior art device is that no means is provided for changing the force required to insert and rotate mountings such as the bayonet mount of the prior art. This may present a difficulty for users who prefer easier and faster changing telescopes 121, 123.